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Hello,the frontal area caculations i did were done using a front view photo of the car place onto some graph paper and scaled to size.
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What was the result of this calculation? Even [overall height]*[overall width]*[0.85 packing factor] would do for now.
You point out that for a 20% efficient engine, 80% of the energy of the gasoline is lost. True, but very few of us on the forum run 20% efficient engines. Read
this article for info on how to convert BSFC to % efficiency and some insight into what is possible in the efficiency department.
The Wikipedia article mentions 25% efficiency - 327g/kWh - as a typical "cycle average". That would be the average operating conditions during some driving cycle, perhaps the EPA's. Ecomodders' engines as a group do much better than this. See the
BSFC maps. Neglecting lean burn, my engine peaks at 215g/kWh, and if you can keep it below 4000RPM, you can keep it below 250g/kWh all day. Still, the car only delivers 57mpg according to the EPA. 37% thermodynamic efficiency does not get you to 100mpg, it gets you to 57 EPA mpg = 70mpg in careful hands.
And no, I do not believe that waste heat recovery can recover 20% of what was lost the first time around. If you can get 10% (for a 30% fuel economy boost), you're doing amazingly well. You should pursue it, and discuss your methods and results here, but do not expect miracles.